fix(plugin-coverage): skip invalid line numbers from tools like pytest-cov

Author: matejchalk

packages/plugin-coverage/src/lib/runner/lcov/lcov-runner.ts

@@ -77,13 +77,18 @@ export async function parseLcovFiles(
           );
         }
         const parsedRecords = parseLcov(toUnixNewlines(lcovFileContent));
-        return parsedRecords.map<LCOVRecord>(record => ({
-          ...record,
-          file:
-            typeof result === 'string' || result.pathToProject == null
-              ? record.file
-              : path.join(result.pathToProject, record.file),
-        }));
+        return parsedRecords.map(
+          (record): LCOVRecord => ({
+            title: record.title,
+            file:
+              typeof result === 'string' || result.pathToProject == null
+                ? record.file
+                : path.join(result.pathToProject, record.file),
+            functions: filterOutInvalidLines(record, 'functions'),
+            branches: filterOutInvalidLines(record, 'branches'),
+            lines: filterOutInvalidLines(record, 'lines'),
+          }),
+        );
       }),
     )
   ).flat();
@@ -95,6 +100,26 @@ export async function parseLcovFiles(
   return parsedResults;
 }
 
+/**
+ * Filters out invalid line numbers.
+ *
+ * Some tools like pytest-cov emit line number 0. https://github.com/nedbat/coveragepy/issues/1846
+ *
+ * @param record LCOV record
+ * @param type Coverage type
+ * @returns Coverage output from record without invalid line numbers
+ */
+function filterOutInvalidLines<T extends 'branches' | 'functions' | 'lines'>(
+  record: LCOVRecord,
+  type: T,
+): LCOVRecord[T] {
+  const stats = record[type];
+  return {
+    ...stats,
+    details: stats.details.filter(detail => detail.line > 0),
+  };
+}
+
 /**
  * This function aggregates coverage stats from all coverage files
  * @param records LCOV record for each file

packages/plugin-coverage/src/lib/runner/lcov/lcov-runner.unit.test.ts

@@ -31,13 +31,26 @@ LH:1
 BRF:0
 BRH:0
 end_of_record
+`;
+
+  const PYTEST_REPORT = `
+TN:
+SF:kw/__init__.py
+DA:1,1,gG9L/J2A/IwO9tZM1raZxQ
+DA:0,0,gG9L/J2A/IwO9tZM1raZxQ
+LF:2
+LH:1
+BRF:0
+BRH:0
+end_of_record
 `;
 
   beforeEach(() => {
     vol.fromJSON(
       {
         [path.join('integration-tests', 'lcov.info')]: UTILS_REPORT, // file name value under SF used in tests
         [path.join('unit-tests', 'lcov.info')]: CONSTANTS_REPORT, // file name value under SF used in tests
+        [path.join('pytest', 'lcov.info')]: PYTEST_REPORT,
         'lcov.info': '', // empty report file
       },
       'coverage',
@@ -106,4 +119,19 @@ end_of_record
       )}.`,
     );
   });
+
+  it('should skip lines numbered 0', async () => {
+    await expect(
+      parseLcovFiles([path.join('coverage', 'pytest', 'lcov.info')]),
+    ).resolves.toEqual([
+      expect.objectContaining({
+        lines: expect.objectContaining({
+          details: [
+            { hit: 1, line: 1 },
+            // no { hit: 0, line: 0 },
+          ],
+        }),
+      }),
+    ]);
+  });
 });